[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: GSBN:Re: : slab edge insulation

I don't think I said don't use edge insulation for radiant slabs
(whereas I might have said that for normal slabs), I said you could get
away from sub slab insulation if you insulated the perimeter walls.  If
you do a radiant slab, even 1/2" of foam between the slab and foundation
wall will work wonders, although 1" is better.
I know that the slab edge in a normal building looks quite bright on a
IR camera (not necessarily equal to total energy loss, just concentrated
energy loss), and that this is a sensible place to insulate, but I don't
think it makes that much of a difference to annual energy cost for
places with 3 or 4000 HDD. When you radiantly heat the slab and/or are
in a cold climate (starting at 6 - 8000 HDD) you should at least do the
perimeter walls.

Why is it again that we cant insulate between the stem wall and the

John Straube
Dept of Civil Engineering and School of Architecture
University of Waterloo
Waterloo, Canada

-----Original Message-----
From: GSBN [mailto:GSBN@...] On Behalf Of Nehemiah
Sent: March 10, 2003 23:07
Subject: Re: GSBN:Re: : slab edge insulation

I beg to differ with John and John.  I did a fair amount of infrared 
camera work a number of years ago to see where heat exits a building in 
central California.  We would crank the heating system up to a little 
bit above what one would normally heat a house to, and then film it 
from the outside in the middle of the night.  The three greatest loss 
sites for a "normally" insulated house (one that just meets the minimum 
California requirements), were (1) the aluminum frames of windows, (2) 
the slab edge, and (3) hot water pipes and other pipes (e.g., the 
pop-off valve) near the water heater.  Slab edges, when the slab is 
exposed to the night sky, account for a VERY significant portion of the 
winter heat losses.  Slab edges, when they are tucked under a very wide 
eave, account for a lot less.  And slab edges that are insulated, very 
much less still.  If a person is going to have a a radiant floor 
heating system, then they absolutely should insulate the slab edge.  
There are products available that have a hard styrene material 
surrounding the insulation.  The hard coating (1) looks good, and (2) 
has a key that ties into the slab so that termites cannot pass between 
the two building elements.  The insulation is used as the form when 
pouring the slab.

Nehemiah Stone

On Tuesday, March 4, 2003, at 05:22 PM, John Swearingen wrote:

> I agree with John Straube about not using slab insulation in SUNNY 
> California.  We have areas that have severe winters and deep frosts, 
> but in most areas we are designing for cooling loads more than 
> heating. Experience, as well as computer simulations, show about a 5F 
> lowering of
> ambient  temperatures for four or five summer months when slab 
> insulation is
> removed.  The corresponding increase in heating loads is usually 
> minimal and
> only significant for a couple of months.
> John
> -----Original Message-----
> From: GSBN [mailto:GSBN@...]On Behalf Of John
> Straube
> Sent: Tuesday, March 04, 2003 1:35 PM
> To: 'GSBN'
> Cc: bainbrid@...
> Subject: RE: GSBN:Re: : slab edge insulation
> I would not use any insul below slabs in sunny california, but would
> use
> it on the stem wall.
> Protection is easy -- you plaster bales? Well you can plaster the foam
> too. The termites are a bigger issue, best solved IMHO with a peel and
> stick over the concrete and down the face of the foam/Mineral fiber
> then plaster over.
> -----Original Message-----
> From: GSBN [mailto:GSBN@...] On Behalf Of Bob 
> Bolles
> Sent: March 4, 2003 12:11
> To: GSBN
> Cc: bainbrid@...
> Subject: RE: GSBN:Re: : slab edge insulation
> Hi John
> You wrote"
> <snip>
>> "Finally, if you are using a concrete foundation, adding a couple 
>> inches
> of foam or fiber insulation to the exteiror of the foundation is 
> likely to be easier and high performance"
> Well, therein lies the problem
> If you place the foam on the exterior, first there is the appearance 
> issue, as well as protecting it from damage. Then, I have to ask if 
> this would potentially provide a path, behind the foam or through it, 
> for termites, ants and other little critters?
> I believe that insulation under the slab is probably appropriate for 
> cold climates, but I am working in sunny Southern California. How much

> insulation should we use, if any, below the slab.
> Regards
> Bob
> Bob Bolles
> Sustainable Building Solutions
> Bob@...
> www.StrawBaleHouse.com
>  "They that can give up essential liberty to obtain a little temporary

> safety deserve neither liberty nor safety"  Benjamin Franklin
> ----
> For instructions on joining, leaving, or otherwise using the GSBN 
> list, send email to GSBN@...HELP in the 
> SUBJECT line.
> ----
> ----
> For instructions on joining, leaving, or otherwise using the GSBN
> list, send
> email to GSBN@...HELP in the SUBJECT line.
> ----
> ----
> For instructions on joining, leaving, or otherwise using the GSBN
> list, send email to GSBN@...HELP in the 
> SUBJECT line.
> ----